Once you summon Destiny HERO - Plasma, Alexis's monsters' effects are negated, meaning Destiny HERO - Plasma won't be destroyed or sent to the graveyard by the effects of her Cyber Angel Dakini or Cyber Gymnast.

If you don't have Desert Twister, add one more Secret Pass to Treasure. The first one will be negated by Alexis' Spell Shield Type-8, then the second one will be successfully activated.

Dark Paladin (7-8k)

Special summon Dark Paladin in DEF position as soon as possible using skills like Balance and Restart. Dark Paladin's effect can negate the activation of any spell card by discarding 1 hand, meaning Alexis' can't perform ritual summon. Note that Alexis uses the effect of Cyber Gymnast to destroy your Dark Paladin if it is ATK position.

Use King of the Swamp depending on what you need. You can send it to the Graveyard to get Polymerization or use it as a Fusion Substitue. It's recommended to have more copies of this card and replace other Fusion Substitute monsters.

You D-gate your wall when she summons Dakini. However, Dakini, and potentially other angels, still has potential to go over your wall with Freya or Idaten; that's when Massive Morph comes into play. Once morphed, the angel can't declare direct attack and AI won't attack unless they know they can beat the monster coming from the gate. That causes the lock down.

After that you just stall and morph whatever monster you've morphed a few more times. Double morphing will 'almost' guarantee that monster will get you over 10k damage, triple will totally seal the deal.

On last turn, storm your d-gate to get back your wall, watch out for spell shield and avoid blowing her BBS, then e-con take the massive thing and UA-Vassal or just Riryoku-Piranha.